Electroacoustic components can be used in RF filter circuits, e.g., mobile communication devices. In such components, electrode structures convert between electromagnetic RF signals and acoustic waves. The acoustic waves generally propagate in an acoustic track at the interface of a piezoelectric material, e.g., as a surface acoustic wave (SAW), or as a guided bulk acoustic wave (GBAW). Such electroacoustic components are known, for example, from German Patent Application DE 102010034121 or U.S. Publication No. 2012/0038435.
What is problematic about known electroacoustic components is that undesired wave modes, e.g., secondary modes, impair the filter characteristic especially in critical frequency ranges. In the filters in U.S. Publication No. 2012/0038435, additional resonators or additional dielectric layers are provided in order to suppress undesired modes, e.g., at frequencies above a passband.
Additional layers make production more expensive and additional resonators make production more expensive and increase the space requirement of corresponding components.